1. Field of the Invention
The invention relates to a technique addressed to the consumption of power, which is correlated to the control of heat of a fixing device provided within a printer.
2. Description of the Related Art
A laser printer has heretofore been known wherein an electrostatic latent image is formed on a photosensitive drum and developed by toner. The developed toner image is transferred onto a sheet of printing paper and then supplied to a fixing device, maintained at a predetermined temperature, where the transferred image is fixed on a sheet of paper by heating.
A heat roller of the fixing device is provided with a heater. Further, the heat roller is heated by supplying power to the heater. However, the maintenance of the temperature of the heat roller used in the fixing device, at a fixable predetermined temperature, is inefficient in terms of power consumption.
When data is not received from a receiving means within a predetermined time interval, control for restraining the supply of power to the fixing device or stopping its supply, to thereby reduce the power being consumed, is performed. While the power being consumed is still in a controlled state (hereinafter called a "power-saved state"), the fixing device is reduced in temperature. Therefore, when the printing is performed under this state, a failure in printing occurs. Thus, the supply of the power to the fixing device is resumed upon printing and the temperature of the fixing device must be controlled so as to return to the predetermined temperature. In this case, however, the time for resuming the supply of the power to the fixing device has been established, up to now, as standard at the time when a data receiving means receives data from a host computer.
However, the received data are not necessarily limited to print data alone. The received data include, for example, control data and data about the shape of each font used for printing. Even when such data, irrelevant to an actual print executing process, are received, the supply of the power to the fixing device is resumed and the temperature of the fixing device is brought to the predetermined high temperature. Therefore, the prior art printers do not efficiently control the power to be consumed.
When the temperature of the fixing device is changed from the low temperature, for saving power, to the predetermined high temperature, a large amount of power is required. Therefore, a problem arises in the excessive response to all received data, thereby frequently controlling the temperature of the fixing device and increasing the power consumed.